DESCRIPTION (Adapted from the application) This core will provide the program project investigators access to state-of-the-art optical microscopic facilities that individual laboratories cannot sustain independently. The core will provide instrumentation for 1. Laser and disk scanning confocal microscopy for high resolution 3-dimensional imaging of parameter-sensitive fluorophore and fluorescent proteins to monitor ions, electrical potentials, oxygen radical generation, pyridine nucleotide reduction, mitochondrial and plasmalemmal membrane permeability, intracellular gene expression and protein translocation, cell viability (apoptosis and necrosis), and other physiological variables. 2. Multiphoton fluorescence microscopy for repeated nondestructive 3-dimensional fluorescence imaging, especially of fragile UV-excited fluorophores such as NAD(P)H and Indo-1, and for serial sectioning through the entire thickness of specimens. 3. Spectroscopy (spectrophotometers, spectrofluorometers), multiwell plate reading and tissue culture (hoods and incubators) for spectral characterization of fluorophores and fluorescent proteins, complementary parallel studies in multiwell plates, and cell maintenance in culture prior to microscopy. 4. Digital darkroom for digitizing images, analyzing and labeling these images, and printing the processed imaging as photographic quality prints and slides for use in publications, reports and oral presentations. 5. Specimen preparation for and imaging by scanning and transmission electron microscopy. In addition, core staff will perform daily maintenance and alignment of the microscopes and provide technical support and training in confocal microscopy, multiphoton microscopy and related techniques to project investigators.